The transport of a slurry comprising a moving fluid carrying suspended solid particles through a closed conduit or pipeline has long been known in the mining, energy, chemical and related industries. It is well know that slurry pipelines are prone to wear in service. Slurry pipelines often incorporate linear pipe segments arranged end to end as well as non-linear pipe bends or “elbows”, which join the linear or straight pipe sections to one another at various angles, to alter the direction of flow of the material being conveyed within the pipeline. When a moving fluid carrying suspended solid particles is forced to change direction, it is easier to change the direction of flow of the fluid than it is to change the direction of the movement of the suspended solid particles. When the particulate material being transported in slurry form is abrasive in nature and the direction of flow of the slurry is altered, it is well established that wear of the interior sidewalls of the elbow occurs, as the suspended solid particles tend to continue to travel on their original straight line trajectory and impinge on the internal wall(s) of the elbow causing erosion or wear. When the damage caused by wear is sufficiently high, the elbows require replacement or repair.
Attempts have been made in the past to reduce or eliminate the erosion of non-linear slurry pipe segments or elbows. Some attempts are based on altering the shape of the elbow. By way of example, U.S. Pat. No. 4,387,914 discloses an elbow having an enlarged vortex chamber aligned with the entry axis to collect material and to form a vortex within the chamber thereby preventing conveyed material from hitting the walls of the elbow by causing it to deflect off—the soft-plug of—material already collected in the chamber. U.S. Pat. No. 4,995,645 describes an elbow in which a section of the elbow between an inlet and outlet opening has a cross-sectional area that is at least 1.5:1 greater than the cross-sectional area of the inlet and outlet openings in an attempt to reduce the wear of the elbow wall caused by the material conveyed therein. U.S. Pat. No. 4,641,864 and U.S. Pat. No. 4,767,243 disclose pipe bends or elbows which cause the conveyed material to form a cushion of that material to prevent erosion of the walls of the conveying system. U.S. Pat. No. 1,518,705 discloses a pipe having a plurality of corrugations cast integral with the interior walls of said pipe. The corrugations are positioned with an angle less than 180 degrees in the upper and lower portions of said pipe.
The most commonly adopted approach to addressing this problem is the use of a liner positioned within the elbow segment of the pipe and fabricated from an elastomeric material to absorb the impact of the particles or fabricated using a material having a higher level of abrasion or erosion resistance than the remainder of the pipe. Examples of such solutions are described in: U.S. Pat. No. 4,199,010; U.S. Pat. No. 4,554,721; U.S. Pat. No. 4,733,889; U.S. Pat. No. 3,350,832; and, U.S. Pat. No. 1,246,189. The devices disclosed in the afore-mentioned patents differ from one another principally in the selection of the material of construction of the liners, and in the manner of affixing the liners to the elbow. The use of a separate liner incorporated into an elbow can be relatively expensive, depending on the cost of the materials of construction, and does not stop the occurrence of significant wear over an extended period of time. The removal and subsequent replacement of the liner can be difficult and costly, requiring the pipeline to be taken off-line to allow access to the liner which can lead to a loss in production.
For the foregoing reasons, there remains a need to provide a pipe fitting for slurry transporting pipes and pipe lines which has improved wear and abrasion resistance.